In the prior art, Japanese Patent Laid-Open No. 8-80797 and No. 10-315894, for example, disclose devices for protecting the knees of a vehicle occupant such as a driver. The airbag device disclosed in the former is located below column cover, and includes an airbag to deploy for protecting the driver from shin to knee when actuated. The airbag device in the latter is located near the column cover below steering wheel, and includes an airbag to deploy for protecting the driver from lower side of the knee to the vicinity of toe when actuated.
However, these knee protection airbag devices have a room for improvement in inflating the airbags effectively along with the course of time from the start to completion of airbag deployment to protect the knees of the occupant.